greater amberjack larval husbandry

The tasks will address (a) the development of appropriate feeding strategies, (b) the effect of the rearing environment during larval rearing and (c) the development of an appropriate industrial protocol for the larval rearing of greater amberjack.

Task 15.1 Effect of feeding regime and probiotics. The effect of different live prey protocols with probiotics and immunostimulants as health promoting/nutritional supplements will be evaluated. The stimulation of the larval immune system by using probiotics and immunostimulants is a promising tool to increase survival rates at early stages of fish. Probiotics such as Shewanella genus, increases in vivo pathogen resistance and promotes an advanced and synchronized metamorphosis and a significantly higher growth. In addition, various studies have shown that the inclusion of dietary Echium oil modulates the stress response of species. Several of these probiotic-immunostimulat substances will be assayed using live preys as vector. Results will be evaluated in terms of survival, growth, development, skeletal deformities and larval nutritional condition. Larvae will also be examined for oxidative stress in terms of production of reactive oxygen species, peroxidative status (measured as thiobarbituric acid reactive substances), antioxidant defense enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and humoral parameters of the immune system. The ontogeny of the digestive enzymes of amberjack larvae focusing on total protease, lipase, amylase and ATPase activities will be also performed.Task 15.2Comparison of semi-intensive and intensive rearing.

Sub-task 15.2.1 (HCMR) Comparison between intensive (in RAS with 500 l tanks) and semi-intensive (Mesocosm with 40,000 l) tanks in triplicate trials where each has a duration of 30 days, which is the period required to undergo metamorphosis. Each system will be evaluated in terms of: (i) ontogeny of visual system through histological procedures, (ii) larval oxidative stress through the activity of specific enzymes, (iii) investigating the larval somatotropic axis (consisting of the growth hormone-releasing hormone, growth hormone, growth hormone receptor, insulin-like growth factors, associated carrier proteins and receptors) that represents the endocrine and autocrine regulator for skeletal muscle growth.

Sub-task 15.2.2 The effect of stocking density on larval performance in terms of growth, survival, skeletal deformities and gene expression of stress and skeleton related genes will be studied.Three different larval rearing densities will be evaluated in triplicate tanks for a period of 30 days.

Sub-task 15.2.3 Ontogeny of the digestive system of greater amberjack larvae (from Actions 15.2.1 and 15.2.2) focusing on proteases, lipases, amylases and ATPase.

Task 15.3 Effect of environmental parameters during rearing.

Sub-task 15.3.1 The effect of tanks hydrodynamics will be studied. Based on results of 15.2, two different tank types; 40,000 l cylindrical vs 2,000 l cylindro-conical will be tested in duplicates for a period of 30 days. The hydrodynamics of the tanks will be also considered after analyzing the current profile. The effect of tank type on larval performance in terms of growth, survival, histology, biochemical composition, skeletal deformities and gene expression of stress and skeleton related genes will be recorded.

Sub-task 15.3.2 Effect of light on larval rearing. Two light intensity ranges and 2 photophases will be tested. The effect of light will be evaluated in terms of larval growth, survival, quality and size dispersion. In addition, the somatotropic axis, growth hormone, growth hormone receptor, insulin-like growth factors and associated carrier proteins will be investigated together with the receptors that represent the endocrine and autocrine regulators for skeletal muscle growth and are known to play key roles in the regulation of metabolism and physiological processes.

Task 15.4 Development of industrial protocol.

Sub-task 15.4.1 Development of an industrial protocol for larval rearing based on the results of the previous tasks. In order to determine larva and fry quality, fish will be sampled periodically during rearing to evaluate growth parameters, development, skeletal deformities and larval nutritional condition (RNA/DNA ratio). In addition, other parameters will be measured such as reactive oxygen species, peroxidative status, antioxidant defence enzymes and humoral parameters of the immune system.

Sub-task 15.4.2 Ossification pattern and incidence of skeletal deformities for amberjack larvae will be evaluated under different levels of intensification. Samples of amberjack larvae from hatching to the end of metamorphosis will we collected at regular intervals, to evaluate ossification pattern. Staining protocols to evaluate these samples will be determined in the project. The ossification and deformity results will be expressed as a function of size and not age as abnormal skeletal development may vary with the growth rate of individuals.

Sub-task 15.4.3 Validation of the developed protocol initially at FCPCT and over two successive years in an SME hatchery.